Magnetic recording apparatus

ABSTRACT

According to one embodiment, a magnetic recording apparatus includes a magnetic recording medium for perpendicular magnetic recording system, a magnetic head including a read head to read data from the magnetic recording medium, and an actuator to actuate the magnetic head on the magnetic recording medium. The magnetic recording medium includes a first magnetic pattern recorded in a servo area by applying a magnetic field horizontally to a disk surface, and the first magnetic pattern corresponding to positioning data used for positioning the magnetic head. The magnetic recording medium further includes a second magnetic pattern recorded in the servo area by applying a magnetic field perpendicularly to the disk surface, and the second magnetic pattern corresponding to position correction data used for correcting the positioning data. The position correction data is derived from modulated original position correction data. The original position correction data is created for correcting the positioning data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-144145, filed Jun. 24, 2010; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic recordingapparatus including a magnetic recording medium for perpendicularmagnetic recording system.

BACKGROUND

The magnetic disk used for magnetic disk drive has been shifting fromconventional horizontal (in-plane) magnetic recording system toperpendicular magnetic recording system for higher capacity.

At the same time, servo data recording is performed by using a devicecalled as a servo track writer (STW). According to the recent highrecording density, time required for recording servo data increases moreand more, and hence the reduction of tact time is desired.

Then, instead of using the STW, using a magnetic transfer method hasattracted interests, since it collectively records the servo data in amagnetic disk by using a master recording medium in which servoinformation is previously patterned.

The magnetic transfer system with respect to a perpendicular magneticrecording medium includes a perpendicular magnetic recording systemwhich perpendicularly apply a magnetic field to a medium surface, and ahorizontal magnetic recording system which horizontally apply a magneticfield to the medium surface. In general, the horizontal magneticrecording system has a preferable transfer characteristic with respectto a pattern miniaturization accompanied by high recording densitycompared with the perpendicular magnetic recording system.

At the same time, with high recording density of a magnetic disk drive,the requirement for track positioning accuracy of the head become severeyear and year. As a technique for improving the track positioningaccuracy of the head, a method including additionally recordingpositioning correction data in a servo area in which data ispreliminarily recorded is given.

The waveform of reproduced data recorded by perpendicular magneticrecording system is rectangle same as the reproduced waveform of datarecoded by magnetic head. Therefore, a compatibility of reproducedwaveform between the data preliminarily recorded in the servo area byperpendicular magnetic recording system and the positioning correctiondata additionally recorded in the servo area by magnetic head isassured.

On the contrary, a reproduced waveform of data recorded by horizontalmagnetic recording system is different from the reproduced waveform ofdata recorded by magnetic head. Horizontal magnetic recording system hasan advantage over realizing higher recording density than perpendicularmagnetic recording system. Therefore, the compatibility of reproducedwaveform between the data preliminarily recorded in the servo area byhorizontal magnetic recording system and the positioning correction dataadditionally recorded in the servo area by magnetic head is not assured.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of theembodiments will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrate theembodiments and not to limit the scope of the invention.

FIG. 1 is an exemplary view schematically showing a magnetic disk ofperpendicular magnetic recording system according to a first embodiment.

FIG. 2 is an exemplary view schematically showing an example of a servopattern.

FIG. 3 is a waveform chart showing a read signal when a positioning datapattern is reproduced at suitable channel setting.

FIG. 4 is an exemplary waveform chart showing a read signal when aposition correction data pattern is reproduced at suitable channelsetting.

FIG. 5 is an exemplary view to explain position correction data(modulation position correction data) recorded in a magnetic disk of thefirst embodiment and modulated position correction data reproduced fromthe magnetic disk of the first embodiment.

FIG. 6 is an exemplary view to explain a shift amount corrected byposition correction data.

FIG. 7 is an exemplary view to explain position correction data(original position correction data) recorded in a magnetic disk of acomparative example and position correction data reproduced from themagnetic disk of the comparative example.

FIG. 8 is an exemplary view showing modulation position correction datawith a redundancy bit according to the first embodiment.

FIG. 9 is an exemplary view to explain an effect obtained by usingmodulation position correction data with the redundancy bit according tothe first embodiment.

FIG. 10A and FIG. 10B are exemplary views to explain another modulationposition correction data according to the first embodiment.

FIG. 11A and FIG. 11B are exemplary views to explain still anothermodulation position correction data according to the first embodiment.

FIG. 12 is an exemplary view schematically showing the magnetic diskdrive according to the first embodiment.

FIG. 13 is an exemplary view showing a substantial part of a magneticdisk drive according to a second embodiment.

FIG. 14 is an exemplary view to explain a function of the magnetic diskdrive according to the second embodiment.

FIG. 15 is an exemplary view schematically showing a magnetic disk driveaccording to a third embodiment.

FIG. 16 is an exemplary view to explain a function of the magnetic diskdrive according to the third embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings.

In general, according to one embodiment, a magnetic recording apparatusincludes a magnetic recording medium for perpendicular magneticrecording system, a magnetic head including a read head configured toread data from the magnetic recording medium and an actuator configuredto actuate the magnetic head on the magnetic recording medium. Themagnetic recording medium includes a first magnetic pattern recorded ina servo area by applying a magnetic field horizontally to a disksurface, and the first magnetic pattern corresponding to positioningdata used for positioning the magnetic head. The magnetic recordingmedium further includes a second magnetic pattern recorded in the servoarea by applying a magnetic field perpendicularly to the disk surface,and the second magnetic pattern corresponding to position correctiondata used for correcting the positioning data. The position correctiondata is derived from modulated original position correction data, theoriginal position correction data is created for correcting thepositioning data.

(First Embodiment)

FIG. 1 is a view schematically showing a magnetic disk (magneticrecoding medium) of perpendicular magnetic recording system according toa first embodiment.

A magnetic disk of the present embodiment includes a data area 2 and aservo area 3. The data area 2 is an area in which arbitrary user data isrecorded by user. The servo area 3 is an area in which a servo patternis recorded. The servo pattern comprises North and South Pole magneticpatterns.

In FIG. 1, there is shown a state that a plurality of arc-like servoareas 3, which extend from the rotational center of the magnetic disk 1to a radius direction, is radially arranged. The shape and arrangementof the servo area 3 are not limited to FIG. 1.

FIG. 2 schematically shows an example of a servo pattern.

A servo pattern 4 includes patterns (first magnetic patter) 5 to 7 and apattern (second magnetic pattern) 8. The patterns 5 to 7 correspond topositioning data used for positioning a magnetic head. The pattern 8corresponds to position correction data used for correcting thepositioning data.

The pattern 5 includes a magnetic pattern corresponding to data relatedto a preamble and a servo mark. The pattern 6 includes a magneticpattern corresponding to data related to an address. The pattern 7includes a magnetic pattern corresponding to data related to a burst.

Hereinafter, a pattern corresponding to positioning data used forpositioning a magnetic head is called as a positioning data pattern.Moreover, a pattern corresponding to position correction data used forcorrecting positioning data is called as a position correction datapattern.

Positioning data patterns 5 to 7 are recorded in a servo area in such amanner that a master disk is closely attached to a perpendicularmagnetic recording medium, and a magnetic field is horizontally appliedto the disk surface. The positioning data patterns 5 to 7 are reproducedby a suitable magnetic head (suitable channel setting). In this case,the read signal has a spike shape similar to an in-plane recordingwaveform as can be seen from FIG. 3.

The position correction data pattern 8 is recorded in a servo area usinga magnetic head after positioning data patterns 5 to 7 are recorded. Inthis case, the magnetic head applies a magnetic field perpendicularly tothe disk surface. When the position correction data pattern 8 isreproduced by suitable channel setting, the read signal has arectangular waveform shown in FIG. 4.

From the signal waveforms shown in FIG. 3 and FIG. 4, it can be seenthat suitable channel setting for demodulating data is different betweenpositioning data patterns 5 to 7 and the position correction datapattern 8. In general, demodulation of positioning data patterns 5 to 7is preferentially carried out. For this reason, the position correctiondata pattern 8 is to be read by using channel setting suitable forpositioning data patterns 5 to 7.

FIG. 5 is a view to explain position correction data (modulationposition correction data) recorded in a magnetic disk of the presentembodiment and modulated position correction data reproduced from themagnetic disk of the present embodiment.

According to a well-known method (e.g., the specification of U.S. Pat.No. 6,608,731B2), position correction data is created. For example, asshown in FIG. 6, the position correction data (original positioncorrection data) created by the method is data for correcting a shiftamount 13 of a magnetic head 10 from the track center 12 at the time oftracing track 11 by the magnetic head 10.

Here, if the original position correction data is recorded in themagnetic disk 1 as a magnetic pattern (hereinafter, referred to as anoriginal position correction data pattern) and this recorded originalposition correction data pattern is read by cannel setting suitable forpositioning data patterns 5 to 7 (comparative example), then theoriginal position correction data pattern is reproduced in error(reproduction error) as shown in FIG. 7 for instance, since the channelsetting data read characteristic is not suitable for the originalposition correction data pattern.

So, in the present embodiment, the original position correction data ismodulated (corrected) such that the original position correction data isacquired even if the channel setting suitable for positioning datapatterns 5 to 7 is used. Therefore, according to the present embodiment,it is possible to simply and accurately reproduce the data in the servoarea (positioning data patterns 5 to 7, position correction data pattern8) in which the data is to be reproduced by different waveform.

In the example of FIG. 5, the original position correction data aftermodulation (modulated position correction data) differs from theoriginal position correction data by one bit. In the present embodiment,the modulated position correction data is recorded as a positioncorrection data pattern 8 in the magnetic disk, and not the originalposition correction data.

The information required for modulation (modulation information) ispreviously acquired. For example, a comparison is carried out betweenthe following reproduction signals to previously acquire theinformation. One is a reproduction signal (erroneous reproductionsignal) of the original position correction data pattern read by channelsetting suitable for positioning data patterns 5 to 7. The other is areproduction signal (correct reproduction signal) of the originalposition correction data read by channel setting suitable for theposition correction data pattern 8.

The modulation information is, for example, provided in a form of tablein which the original position correction data before modulation (whichis to be erroneously reproduced) is associated with the originalposition correction data after modulation (which is to be accuratelyreproduced). In the case of FIG. 5, “010” and “011” are associated, andthen, registered in the table.

Another modulation will be described below with reference to FIG. 8.

In the example of FIG. 5, the number of bits of the original positioncorrection data is the same before and after the modulation. But, in theexample of FIG. 8, the number of bits of the original positioncorrection data is different before and after the modulation. The numberof bits is increased after the modulation.

The modulation shown in FIG. 8 is generalized as follows. If theoriginal position correction data is set to N-bit (N≧1) data, theposition correction data is derived by adding 2N-bit data to the N-bitdata such that both sides of each of digit of the N-bit data is addedwith bit data having same value as the digit. For example, the modulatedposition correction data corresponding to 3 bits, “010” (originalposition correction data) of FIG. 5 is expressed as 9 bits, “000111000”as shown in FIG. 8.

The effect of the modulation of FIG. 8 will be described below.

When 3 bits are given, there are eight kinds data of “000”, “100”,“001”, “101”, “010”, “110”, “011” and “111”. These eight kinds of 3 bitsdata are recorded in the perpendicular magnetic recording medium by themagnetic head to create eight kinds of magnetic patterns correspondingto eight kinds of 3 bits data.

Investigation is made with respect to the following signal waveforms ofeight kinds of magnetic patterns. One is a signal waveform (rectangularwaveform) reproduced by channel setting suitable for the positioncorrection data pattern. The other is a signal waveform (differentialwaveform) reproduced by channel setting suitable for the positioningdata pattern. FIGS. 9A to 9H show the investigated result. In FIGS. 9Ato 9H, a white circle ∘ shows a point (sampling point) at which amodulated value (reproduced value) is the same on a rectangular waveform(upper-side waveform) and a differential waveform (lower-side waveform),and a black circle ● shows a point (sampling point) at which a modulatedvalue (reproduced value) may be different on the rectangular waveformand the differential waveform (lower-side waveform).

From FIGS. 9A to 9H, in a case where the 3 bits data are “000” and“111”, the center value (second digit value) and its both side values(first and third digit values) are the same in both of the rectangularand differential waveforms. Therefore, in a case where the originalposition correction data is “0”, an occurrence risk of the reproductionerror is sufficiently reduced by demodulating the modulated correctiondata “000” which is obtained by adding the same value (0) to both sidesof “0”, and employing its the center value (0) as the reproductionvalue. Likewise, when the original position correction data is “1”, thereproduction error is sufficiently reduced by demodulating the modulatedcorrection data “111” which is obtained by adding the same value (1) toboth sides of “1”, and employing its the center value (1) as thereproduction value.

From FIGS. 9A to 9H, it can be seen that the center values of therectangular and differential waveforms are the same whereas the valuesof both sides of the center value are different when 3 bits data are“001” and “110”. In this case, it is possible to prevent erroneousdemodulation by using Vitabi decoding.

From FIGS. 9A to 9H, it can be seen that the center values of therectangular and differential waveforms are different when 3 bits dataare “100”, “101”, and “011”. In this case, it is highly impossible toprevent erroneous demodulation even if Vitabi decoding is used.

From the above description, the 3N-bit modulated position correctiondata is said to have an advantageous data structure with low occurrencerisk of the reproduction error, in which the 3N-bit modulated positioncorrection data is obtained by the technique (both sides same valuemodulation) including providing 2N-bit data to the original positioncorrection data of N-bit such that both sides of each of digit of theoriginal position correction data is added with bit data having samevalue as the digit.

In the both sides same value modulation, one same bit value is added toeach of both sides, but as shown in FIGS. 10A and 10B, two same bitvalues may be added to each of both sides for instance. Further, threesame bit values or more may be added.

In addition, from FIGS. 9A to 9H, in the cases where 3 bits data are“001” and “110”, the center value and one side value are correctlydemodulated. Therefore, 2N-bit modulated position correction data issaid to have an advantageous data structure with low occurrence risk ofthe reproduction error, in which the 2N-bit modulated positioncorrection data is obtained by the technique (one side same bitmodulation) including providing N-bit data to the original positioncorrection data of N-bit such that left side of each of digit of theoriginal position correction data is added with bit data having samevalue as the digit.

Furthermore, as shown in FIGS. 11A and 11B, in a case where the originalposition correction data has continuously the same values, a flagindicating the continuity of the same value is set, and thereby, it ispossible to omit the same value bits (redundancy bits) added to bothsides of each digit, resulting in data reduction. In FIGS. 11A and 11B,there are shown six bits original position correction data continuingthe same values, however, the number of bits is not limited to six. Forexample, redundancy bits may be omitted with respect to three bit ormore original position correction data continuing the same values.

The following method is provided as one method of preventing thereproduction error of position correction data. According to the method,although one magnetic head is used, channel setting is changed whenpositioning data patterns 5 to 7 are reproduced and when the positioncorrection data pattern 8 is read. However, a problem relating read timeis remained since changing the channel setting requires time.

The following method is another method of preventing the reproductionerror of position correction data. According to the method, the positioncorrection data pattern 8 is recorded in a data area. The positioncorrection data pattern 8 and user data are reproducible by the samechannel setting, therefore, it is possible to prevent a generation ofreproduction error of the position correction data pattern 8. However,there is a need to remodel a currently using channel circuit so that theposition correction data pattern 8 is recorded in the data area. This isa factor of causing a problem that much time is taken and the costbecomes high. Further, there is a need to find the position correctiondata pattern 8 from patterns recorded in the data area, and toselectively read it. For this reason, a problem arises in read time,too.

In contrast to the methods, according to the present embodiment, theposition correction data pattern corresponding to the modulated positioncorrection data is recorded in the servo area, hence it is possible tosimply and accurately reproduce the servo data from servo patterns(magnetic patterns) recorded in the servo area.

For example, the present embodiment is applicable to a high recordingdensity magnetic disk of perpendicular magnetic recording, which has asize of 2.5 inches and a capacity of 500 Giga or more. In such a highrecording density magnetic disk, it is difficult in the currenttechnique to simply and accurately reproduce the servo data (positioningdata, position correction data) in which the servo data is to bereproduced by different waveforms (recorded by different manner).

FIG. 12 is a view schematically showing a magnetic disk drive (magneticrecording apparatus) according to the present embodiment.

The magnetic disk drive of the present embodiment comprises a magneticdisk 1, a spindle motor 21, a magnetic head 22, an actuator 23, a headamplifier (head IC) 24 and a printed circuit board (PCB) 30.

In the magnetic disk drive shown in FIG. 12, the magnetic disk 1 usingmodulation of employing no redundancy bit shown in FIG. 5 will bedescribed below. The magnetic disk 1 using modulation of employing theredundancy bit shown in FIG. 8 will be described in the following thirdembodiment.

The magnetic disk 1 is rotated by a spindle motor 21 at high speed.

The magnetic head 22 includes a read head 22R and a write head 22W. Theread head 22R reads a servo pattern from a servo area 3 formed on themagnetic disk 1 while reading user data on a user track. The write head22W writes user data onto a data track of a data area.

An actuator 23 is driven by a voice coil motor (VCM), and then, controlsthe attached magnetic head 22 so that the head 22 is moved to the radiusdirection on the magnetic disk. The drive of the voice coil motor iscontrolled by a motor driver 28 mounted on a PCB 30. A head amplifier 24amplifies a read signal (servo pattern and user data) read by the readhead 22R, and then, outputs the read signal to a read/write channel(signal processing unit) 25 mounted on the PCB 30.

The PCB 30 is mounted with a read/write channel 25, a microprocessorunit (CPU) 27, a motor driver 28 and a hard disk controller (HDC) 29.The read/write channel 25 is a signal processing unit, which processes aread/write signals. The read/write channel 25 includes a servocontroller 26, which reproduces servo data from the servo data outputfrom the read head 22R.

The servo controller 26 outputs the reproduced servo data to the CPU 27.It is noted that the servo controller 26 generates position error datafrom a servo burst pattern of the reproduced servo data, and outputs thedata to the CPU 27.

The CPU 27 is a main controller of the magnetic disk drive. The CPU 27executes the positioning control of the magnetic head 22 based on theservo data including the positioning data and the position correctiondata according to the present embodiment.

The motor driver 28 includes a VCM driver and a SPM driver. The VCMdriver supplies a driving current to the voice coil motor of theactuator 23 according to the control of the CPU 27. The SPM driversupplies a driving current to the spindle motor 21.

The HDC 29 is an interface, which executes a data transfer with anexternal host system. The HDC 29 transfers user data output from theread/write channel 25 to the host system based on the control of the CPU27. Further, the HDC 29 receives data from the host system, andtransfers it to the read/write channel 25.

According to the magnetic disk drive of the present embodiment, theservo pattern including the positioning data pattern and the positioncorrection data pattern, which are recorded in the servo area of themagnetic disk, is read by the read head 22R.

The servo data including positioning data corresponding to the servopattern and position correction data read by the read head 22R isreproduced by the read/write channel 25. At this time, the positioncorrection data is accurately reproduced as described above. Inaddition, as the usually used hardware may be employed as the read/writechannel 25, the complication of apparatus structure and the increasingof cost are prevented.

The reproduced servo data is output to the CPU 27. Then, the CPU 27controls the drive of the actuator 23 based on the reproduced servo dataincluding positioning data and position correction data to position themagnetic head 22 on a target data track which is a target position onthe magnetic disk 1. At this time, the positioning data is accuratelycorrected based on the accurately reproduced position correction data.Therefore, the magnetic head 22 can be accurately positioned on thetarget data track.

(Second Embodiment)

FIG. 13 is a view showing a substantial part (read/write channel) of amagnetic disk drive (magnetic recording apparatus) according to a secondembodiment.

The present embodiment differs from the first embodiment in tow points,that is, a magnetic disk and a read/write channel.

First, the magnetic disk will be described below.

The magnetic disk drive of the present embodiment includes a well-knownmagnetic disk, and not the magnetic disk of the first embodiment.

In the magnetic disk of the first embodiment, the position correctiondata pattern is the magnetic pattern corresponding to the positioncorrection data derived from the modulated original position correctiondata. In the well-known magnetic disk, the position correction datapattern is the magnetic pattern corresponding to the original positioncorrection data.

Next, the read/write channel will be described below.

The read/write channel 25 a of the present embodiment includes aposition correction data demodulator circuit 40 for demodulatingerroneously read position correction data into correct data. Theposition correction data demodulator circuit 40 is provided in a servocontroller 26 a.

The demodulation of the present embodiment will be described below withreference to FIG. 14.

According to a well-known method (e.g., the specification of U.S. Pat.No. 6,608,731B2), a position correction data (original positioncorrection data) is created. This original position correction data isrecorded in a servo area as a position correction data pattern using amagnetic head. When the position correction data pattern recorded in theservo area is read and reproduced by channel setting suitable for apositioning data pattern, data “011” different from the originalposition correction data “010” is acquired (reproduction error).

So, in the present embodiment, the position correction data demodulatorcircuit 40 demodulates (corrects) the erroneously reproduced originalposition correction data into correct data. A reproduced servo dataincluding position correction data and demodulated position correctiondata is output to a CPU (not shown) (corresponding to the CPU 27 in FIG.12). The CPU controls the drive of an actuator (not shown)(corresponding to the actuator 23 shown in FIG. 12) based on the servodata including position correction data and demodulated positioncorrection data to position a magnetic head onto a target data trackwhich is a target position on a magnetic, disk. At this time, aspositioning data is accurately corrected based on the positioncorrection data accurately reproduced by demodulation, the magnetic headcan be controlled so that it is accurately positioned on the target datatrack.

The information required for modulation (modulation information) ispreviously acquired. For example, a comparison is carried out betweenthe following reproduction signals to previously acquire theinformation. One is a reproduction signal (erroneous reproductionsignal) of an original position correction data pattern read by amagnetic head (channel setting) suitable for a positioning datapatterns. The other is a reproduction signal (correct reproductionsignal) of an original position correction data read by a magnetic head(channel setting) suitable for the original position correction datapattern.

For example, the demodulation information is provided in a form of tablelike the case of modulation. In this case, the original positioncorrection data (e.g., “010” in FIG. 14) is associated with an erroneousreproduction value of the corresponding original position correctiondata (e.g., “011” in FIG. 14).

As described above, even in case where the magnetic disk drive includesa well-known magnetic disk, by incorporating the position correctiondata demodulator circuit 40, it is possible to simply and accuratelyreproduce the data in the servo area (positioning data pattern, positioncorrection data pattern) in which the data in the servo area is to bereproduced by different waveforms.

(Third Embodiment)

FIG. 15 is a view schematically showing a magnetic disk drive (magneticrecording apparatus) according to a third embodiment.

In the present embodiment, the magnetic disk 1 using modulation by theredundancy bit of the first embodiment and the read/write channel 25 aof the second embodiment are used.

Here, as shown in FIG. 16, the case of using the both sides same bitmodulation will be described. First, a position correction data(original position correction data) is created by well-known method, andmodulated position correction data is obtained by applying the bothsides same bit modulation to the created original position correctiondata. This modulated position correction data is recorded in a magneticdisk 1 as a position correction data pattern.

A servo pattern including the position correction data pattern recordedin the magnetic disk 1 is read by a magnetic head 22, and reproduced asservo data by a read/write channel 25 a. The data corresponding to themodulated position correction data among the reproduced servo data, isdemodulated by a position correction data demodulator circuit 40, andthe original position correction data is acquired. In this case, thedemodulation by the position correction data demodulator circuit 40 iscarried out in manner that a second digit (center) bit (e.g., “0”, “1”,“0” in FIG. 16) is selected every 3 bits data (e.g., “000”, “111”, “000”in FIG. 16). It is noted that in case of one side same bit modulation,the first or second digit bit is selected every 2 bits data.

As described above, in the present embodiment, the magnetic disk 1 isemployed as the first embodiment, it is possible to simply andaccurately reproduce data in the servo area (positioning data pattern,position correction data pattern) in which the data in the servo area isto be reproduced by different waveforms.

In addition, as the magnetic disk 1 utilizes modulation by redundancybits, it is possible to sufficiently reduce the occurrence risk of thereproduction error. Moreover, the magnetic disk 1 using modulation byredundancy bits is usable by a simple change of the apparatus, thecomplication of the apparatus configuration and the increasing of costare suppressed, in which the simple change of the apparatus is using theread/write channel 25 a including the servo controller 26 a having theposition correction data modulating function (position correction datamodulator circuit).

The various modules of the systems described herein can be implementedas software applications, hardware and/or software modules, orcomponents on one or more computers, such as servers. While the variousmodules are illustrated separately, they may share some or all of thesame underlying logic or code.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A magnetic recording apparatus comprising: a magnetic recording medium for perpendicular magnetic recording system; a magnetic head comprising a read head configured to read data from the magnetic recording medium; and an actuator configured to actuate the magnetic head on the magnetic recording medium, wherein the magnetic recording medium comprises a first magnetic pattern recorded in a servo area by applying a magnetic field horizontally to a disk surface, and the first magnetic pattern corresponding to positioning data used for positioning the magnetic head; and a second magnetic pattern recorded in the servo area by applying a magnetic field perpendicularly to the disk surface, and the second magnetic pattern corresponding to position correction data used for correcting the positioning data, wherein the position correction data is derived from modulated original position correction data in which the original position correction data is created for correcting the positioning data.
 2. The magnetic recording apparatus of claim 1, wherein the second magnetic pattern is derived by modulating the original position correction data such that position correction data is to be correct position correction data in which the position correction data is obtained by reading a magnetic pattern by the magnetic head wherein the magnetic pattern corresponds to the original position correction data.
 3. The magnetic recording apparatus of claim 2, further comprises a head control module configured to position the magnetic head on the magnetic recording medium based on servo data which comprises the positioning data corresponding to the first magnetic pattern read by the magnetic head and the position correction data corresponding to the second magnetic pattern read by the magnetic head.
 4. The magnetic recording apparatus of claim 1, wherein the original position correction data is N-bit (N≧1) data, the position correction data derived by modulating the original position correction data is 3N-bit data, the 3N-bit data is obtained by adding bit value to both sides of each of digit of the N-bit data in which the bit value has the same value as the digit.
 5. The magnetic recording apparatus of claim 4, further comprises a head control module configured to position the magnetic head on the magnetic recording medium based on servo data which comprises the positioning data corresponding to the first magnetic pattern read by the magnetic head and the position correction data corresponding to the second magnetic pattern read by the magnetic head.
 6. The magnetic recording apparatus of claim 1, wherein the original position correction data is N-bit (N≧1) data, the position correction data derived by modulating the original position correction data is 2N-bit data, the 2N-bit data is obtained by adding bit value to right or left side of each of the N-bit data in which the bit value has the same value as the digit.
 7. The magnetic recording apparatus of claim 6, further comprises a head control module configured to position the magnetic head on the magnetic recording medium based on servo data which comprises the positioning data corresponding to the first magnetic pattern read by the magnetic head and the position correction data corresponding to the second magnetic pattern read by the magnetic head.
 8. The magnetic recording apparatus of claim 1, further comprises a head control module configured to position the magnetic head on the magnetic recording medium based on servo data which comprises the positioning data corresponding to the first magnetic pattern read by the magnetic head and the position correction data corresponding to the second magnetic pattern read by the magnetic head.
 9. A magnetic recording apparatus comprising: a magnetic recording medium for perpendicular magnetic recording system; a magnetic head comprising a read head configured to read data from the magnetic recording medium; and an actuator configured to actuate the magnetic head on the magnetic recording medium, wherein the magnetic recording medium comprises a first magnetic pattern recorded in a servo area by applying a magnetic field horizontally to a disk surface, and the first magnetic pattern corresponding to positioning data used for positioning the magnetic head; a second magnetic pattern recorded in the servo area by applying a magnetic field perpendicularly to the disk surface, and the second magnetic pattern corresponding to position correction data used for correcting the positioning data; and further comprises a demodulating module configured to demodulate position correction data into correct data, wherein the position correction data is obtained by reading by the magnetic head and the position correction data corresponds to the second magnetic pattern.
 10. The magnetic recording apparatus of claim 6, further comprises a head control module configured to position the magnetic head on the magnetic recording medium based on servo data which comprises the positioning data corresponding to the first magnetic pattern read by the magnetic head and the position correction data corresponding to the second magnetic pattern read by the magnetic head. 